Use of liquid crystals as an additive for lubricants has been studied. For example, Patent Document 1 discloses a method of simply changing a frictional force between two solid bodies by phase transfer of a thermotropic liquid crystal and the like introduced between the two bodies of relatively movable machine components. Patent Document 2 discloses a lubricant composition comprising a base oil, a liquid crystal, and a friction adjusting agent. Patent Document 3 discloses a lubricant composition containing a liquid crystal compound and a fluorinated oil. Patent Document 4 discloses a lubricant composition containing a base oil, an organic molybdenum compound, and a liquid crystal. The Patent Documents 1 to 4 describe that the friction coefficient can be reduced by adding a liquid crystal compound to a lubricant composition.    (Patent Document 1) JP-A-2-503326 (claims)    (Patent Document 2) JP-A-6-128582 (claims)    (Patent Document 3) JP-A-7-82582 (claims)    (Patent Document 4) JP-A-2004-182855 (claims)
In the methods of the Patent Documents 1 to 4, a practically useful effect of reducing the friction coefficient cannot be obtained unless the amount of the liquid crystal in the lubricant composition is 1% or more, and preferably 10% or more. However, a liquid crystal compound is a very expensive material, whereas a lubricant composition must generally be available at a low cost. The addition of a liquid crystal in an amount of 1% or more to a lubricant composition is unprofitable. This is the reason why no lubricant containing a liquid crystal compound is used in practice. There has been no lubricant composition containing an ionized liquid crystal compound.
An object of the present invention is to provide a lubricant additive which can exhibit an effect of reducing the coefficient of friction when added in a small amount, and a lubricant composition and a grease composition containing the lubricant additive.